A Unique Case of Gross Hematuria in a Patient With Ewing Sarcoma.

The standard therapy for Ewing sarcoma, the second most common bone tumor in children, includes alkylating agents such as ifosfamide and cyclophosphamide. One common adverse side effect of such agents is hemorrhagic cystitis, which typically presents with hematuria. We present the case of a patient with Ewing sarcoma who developed persistent gross hematuria followed by severe acute kidney injury while receiving chemotherapy. After interdisciplinary evaluation, including renal biopsy and assessment for lupus nephritis, a unique underlying diagnosis of immune-complex glomerulonephritis was determined. Herein, we discuss this novel case, including stepwise diagnostic evaluation, multimodal therapy, chemotherapy adjustments, and long-term disease monitoring.